Rice (Oryza sativa L.), the staple food in South-East Asian countries, is a water-intensive crop so that its productivity is highly affected by drought, the most severe environmental stress factor. We report here the development of transgenic rice via overexpression of full length OsRab16A (driven by endogenous promoter) or AtDREB1A driven by rd29A promoter in the background of the aromatic indica rice cultivar, Pusa Sugandhi 2 (PS2) through biolistic transformation. Both the transgenes were stably introgretted in T₂ generations as indicated by the results of polymerase chain reaction (PCR). Reverse transcriptase (RT)-polymerase chain reaction (PCR) analyses showed that the expression of both the transgenes was induced by drought stress in all the T₂ transgenic plants examined, which were highly tolerant to water deficit stress during both the vegetative and reproductive stages without their morphological or agronomic traits being affected. Protein immunoblot analysis with Rab16A (= anti dehydrin) antiserum showed detectable accumulation of Rab16A protein in the transgenics in response to drought stress and exogenous abscisic acid (ABA) application. The physiological studies revealed that the expression of the transgene under drought stress in T₂ transgenics was associated with lesser shoot or root length inhibition, improved leaf relative water content, stable maintenance of chlorophyll, lesser hydrogen peroxide accumulation with higher catalase activity and an increased accumulation of the osmoprotectant proline, as compared with the wild type (WT) plants. The transgenic plants also showed significantly higher filled grain, spikelet fertility and grain yield under stressed conditions. All these findings highlighted the tremendous potentiality of both OsRab16A and AtDREB1A in conferring drought tolerance without affecting the normal phenotype and physiology of the plants. To our knowledge, this is the first report on the development of a drought-tolerant transgenic aromatic rice variety through overexpression of genes, one involved in ABA-dependent pathway (OsRab16A), while the other in ABA-independent pathway (AtDREB1A) of stress tolerance, thereby highlighting the significance of both the pathways in drought tolerance of the aromatic rice varieties.

中文翻译：

---

OsRab16A和AtDREB1A的独立过表达在转基因香米品种Pusa Sugandhi 2中表现出增强的耐旱性

稻米（Oryza sativa L.）是东南亚国家的主要食品，是一种水力密集型作物，因此其生产力受到最严重的环境压力因素干旱的高度影响。我们在这里报告了通过过量表达的全长OsRab16A（由内源性启动子驱动）或由rd29A启动子驱动的AtDREB1A在芳香稻品种Pusa Sugandhi 2（PS2）的背景下通过生物弹转化实现的发展。两种转基因均在T ₂中稳定内向如聚合酶链反应（PCR）结果所示。逆转录酶（RT）-聚合酶链反应（PCR）分析表明，在所有受检的T ₂转基因植物中，这两种转基因的表达均受干旱胁迫诱导，在营养和生殖阶段均耐缺水不会影响其形态或农艺性状。用Rab16A（=抗脱水素）抗血清进行蛋白质免疫印迹分析表明，响应干旱胁迫和外源脱落酸（ABA）应用，Rab16A蛋白在转基因物中可检测到积累。生理学研究表明，干旱胁迫下转基因在T _{2中的表达}与野生型（WT）植物相比，转基因植物与较低的芽或根长度抑制，改善的叶片相对含水量，叶绿素的稳定维持，具有较高的过氧化氢酶活性的较少的过氧化氢积累和渗透保护性脯氨酸的积累相关。在胁迫条件下，转基因植物还显示出明显更高的填充谷物，小穗育性和谷物产量。所有这些发现凸显了OsRab16A和AtDREB1A的巨大潜力赋予植物耐旱性而又不影响植物的正常表型和生理。据我们所知，这是关于通过基因过度表达开发耐旱转基因芳香水稻品种的第一份报告，其中一个参与ABA依赖性途径（OsRab16A），而另一个参与ABA依赖性途径（AtDREB1A）耐性，从而突出了这两种途径对芳香稻品种耐旱性的重要性。